1. Field of the Invention
The present invention is generally concerned with electronically metering the histories and periods relevant to the maintenance and use of a printer. The present invention is specifically controlled using a microprocessor to receive certain signals, and to calculate and display certain quantities, particularly concerned with activities within a line printer.
2. Description of the Prior Art
Microprocessor-based control and maintenance panels, sometimes of great sophistication, are known for use with computers. However, metering, or conditions display for printers calls for the accumulation, and display, of certain types of information which are alien to computers.
One such condition which can be metered and displayed for a line printer is the total number of lines printed. In the prior art, such metering of total lines printed was accomplished by a mechanical or by an electrical-mechanical counter.
Another quantity which can be monitored for line printers is the remaining number of hours, or lines, within the life of a replaceable ribbon. This was also accomplished in the prior art by a mechanical or by an electrical-mechanical counter. Such electrical-mechanical counter could either be preset to a fixed number and count down, or, alternatively, could be preset to zero and count up. Both the counters for lines printed and for remaining lines of ribbon life tended to be bulky, expensive and failure prone.
Additionally, prior art printers normally employed an analog "mercury", thermometer-type, powered-on hours indicator. Such indicators are based on the migration of a visual indicator, nominally mercury, through a media during the presence of a potential difference across such media during periods of printer power on. Upon such elapsed hours as the migrating substance has completely crossed the media, the meter scale may be reversed, or the applied voltage may be reversed, and the entire process engaged in in the reverse direction. Unfortunately, the indication of elapsed hours obtained from such devices is extremely crude.
There is no evident attempt in the prior art to accumulate total print hours, possibly because of such crudity of elapsed time indicators. Consequent to the failure to determine total print hours, the duty cycle during which the printer is actually printing, as a fraction of the total hours during which the printer is powered on, has been indeterminable.